Calculator apparatus having a single-step key for displaying and executing program steps and displaying the result

Abstract

A programmable electronic calculator is provided having an LED display device and a single-step key for causing display and execution of individual steps of a program stored in the calculator, and for causing display of the results of said execution by means of a single actuation of the single-step key. As the key is depressed, the next program step that is to be executed is displayed, together with the number of that step in the program. When the key is released, the program step is executed and the result is displayed.

I claim: 
     
       1. A programmable calculator for storing and executing a program having a plurality of program steps, said calculator comprising: keyboard means having a keyboard unit with a plurality of keys for entering data and program steps including a single-step key for initiating single-step operations and having means for generating a signal indicative of said single-step key being depressed and for terminating the generation of said signal, the terminating being indicative of said single-step key being released from it depressed position;   storage means coupled to said keyboard means for receiving and storing entered program steps;   display means for displaying stored program steps, step numbers, and results of executions of said steps; and   processing means coupled to the keyboard means, to the storage means, and to the display means for causing the display means to display a stored porgram step and step number responsive to said signal indicative of depression of the single-step key, and for executing the displayed step and for causing the display means to display the result of said execution in response to the absence of said signal indicative of release of the single-step key from its depressed position.   
     
     
       2. The calculator of claim 1 wherein said keyboard means includes a switching device coupled to said processing means for providing for data and program steps to be entered when the switching device is set to program mode, and for single-step and other operations to be performed when the switching device is set to run mode. 
     
     
       3. The calculator of claim 2 wherein said storage means comprises at least one read-write memory unit coupled to said processing means for receiving and storing data and program steps received via said processing means from said keyboard means during the program mode. 
     
     
       4. The calculator of claim 3 including a read-write program counter for numbering program steps, said read-write program counter being coupled to said processing means and to said read-write memory unit enabling the processing means to access a program step in the read-write memory unit utilizing the content of the program counter as an address of said program step in response to an actuation of the single-step key. 
     
     
       5. The calculator of claim 4 wherein said storage means further comprises at least one read-write memory buffer for temporarily storing program steps received from said read-write memory unit, said read-write memory buffer being coupled to said read-write memory unit and to said processing means for receiving program steps from said read-write memory unit and forwarding said program steps to said processing means. 
     
     
       6. The calculator of claim 5 wherein said means for generating is a keyboard encoder and said signal is a keydown signal, the keyboard encoder providing said keyboard signal and key-identifying signals to said processing means, said keyboard encoder being coupled to said keyboard unit and to said processing means for providing signals to said processing means in response to entries from the keyboard. 
     
     
       7. The calculator of claim 6 further including a read-only memory unit having a routine stored therein for controlling single-step operations, said read-only memory unit being coupled to said processing means and to said keyboard means, a single-step operation being performed in accordance with the stored routine, in response to an actuation of the single-step key. 
     
     
       8. The calculator of claim 7 wherein said display means comprises a display decoder unit coupled to said processing means and an LED output display unit coupled to said display decoder unit for displaying data that is produced by the processing means and formatted for display by the display decoder unit. 
     
     
       9. The calculator of claim 8 wherein: the processing means, in response to the applied keydown signal, first accesses the program step stored in the read-write memory unit at the address corresponding to the step number contained in the read-write program counter, next stores the accessed program step into the read-write memory buffer, then applies the step number and the stored program step to the display decoder unit, and, in response to said stoppage in application of the keydown signal by the keyboard encoder, increments the step number stored in the read-write program counter, executes the program step stored in the read-write memory buffer, and applies the result of said execution to the display decoder unit;   
     
     
       the display decoder unit, in response to application of said step and step number by the processing means, decodes the applied step and step number and, in response to the application of said execution result, decodes the execution result; and 
     
     
       the LED output display unit displays the decoded step and step number in response to the application of said decoded step and step number by the display decoder unit, and displays the decoded execution result in response to application of said decoded execution result by the display decoder unit.